The ability to support current injection specifications (for instance 5 mA) on multiple channels, such as multiple ADC channels, may represent an asset in various devices, e.g., in the automotive area.
A supply voltage configuration such that, for instance, IO (Input/Output) and ADC supplies may be different may represent an appreciated feature in various applications.
A way of complying with such a requirement is to separate an ADC cluster IO ring from the rest of the IO ring such that both rings can be supplied by a dedicated supply unit.
In various applications, the overall current consumption of the ADC plus the ADC IO ring may be small, so that an injected current of, say, 6.5 mA per channel may be at the basis of reliability issues e.g. if the sum of the total injected current exceeds the total consumption on an ADC supply.
An injected current in the input channel may be collected by the supply of the IO ring. If the consumption on the IO ring is lower than the total injected current, then a supply voltage on the IO ring can rise beyond a specification limit, this being possibly the case when an external regulator is of the source type.
U.S. Pat. No. 8,605,398 B1 is exemplary of a solution including a closed loop around a pad terminal. An arrangement as disclosed in that document may be difficult to stabilize insofar as stability may depend on an external capacitance on the pad terminal, which may vary e.g. in a picoFarad to microFarad range. Leakage currents from an additional source and a sink MOS transistor may also limit performance.